Is this an ugly quiz photo, or what! The quiz bird seems to have few field marks, particularly as most of the head and underparts are not depicted, but I guarantee that it is identifiable to species. Given where the bird is perched, it seems straightforward to rule out from consideration all of the non-passerine species. Comparing the branch thicknesses with the obvious dead oak leaves allows us to determine that those branches are not very big, thus, our quiz bird is not very big. That also helps us to rule out non-passerines and at least a chunk of the passerines. [Remember: Passerines – also called perching birds or song birds – occupy the back half, or so, of the field guides, starting – in US/Canada guides, at least – with the flycatchers. Also remember: Neither doves nor woodpeckers are passerines.]
The focus of this quiz photo is on back streaking, a feature overlooked by many when endeavoring to ID birds. That oversight is unfortunate, because it is a very useful ID feature, from both the presence/absence angle and from the particulars of the streaking: color, spacing, thickness, etc. Our quiz bird has black streaking on the back that is variable, with streaks both wide and obvious and thin and not-so-obvious.
Back streaking is a particularly useful ID feature at differentiating various passerine families, at least from the back-is-streaked point-of-view, because there are few passerine families that sport back streaking. In fact, except for a very small number of exceptions, back streaking is restricted in ABA-Area passerines to finches, sparrows, blackbirds, and warblers. Granted, there are a lot of species in two of those families, but both the Passerellidae (New World sparrows, which does not include House and Eurasian Tree sparrows!) and Parulidae (New World warblers) sport species with unstreaked and streaked backs, so the number of streaked-backed species in each is manageable.
Various aspects of upperparts coloration and perch location remove all of the options outside of the four aforementioned passerine families. Well, all of them except one hyper-rare ABA-Area option, and the details of that back streaking and of wing coloration rule out that option: Gray Bunting. The finches can be eliminated from consideration as most finches with gray backs lack streaking there and the one that does have streaking – Black Rosy-Finch – has much longer primary projection.
There are few gray-backed members among the streak-backed sparrow species, and what few there are have much shorter primary projection. The Timberline subspecies of Brewer’s Sparrow provides the closest match among passerellids (members of the Passerellidae), but it sports both brown wings and tail. As for New World sparrows, the Icteridae (New World blackbirds) has few gray-backed members and even fewer that also sport black streaking there. However, tail color and/or wing color eliminate those very few options.
